What is the author's style in For Cause and Comrades: Why Men Fought in the Civil War by James M. McPherson?

McPherson uses a simple style in the text, which is constructed upon answering one single question: Why did the Civil War soldiers fight as intensely and for as long as they did? He divides the book into twelve chapters, the first of which sets up the initial question and divides it into parts. The other eleven chapters suggest and then analyze various hypotheses that answer the question. In each chapter, McPherson finds any one motivational story unconvincing, but he sees merit in each proposal. By the end of the book, McPherson proposes that all of these explanations play an important role and that the historical data cannot show which factors are the weightiest.